1. Field of the Invention
This device relates to radiation sensing and more particularly the measurement and processing of radiometric temperatures. Even more particularly this device determines the thermal contrast between sky and earth for indicating the location of the horizon and the attitude of the device's platform.
2. Description of the Prior Art
Radiometric thermal sensing is not a new concept. There are a variety of radiometric apparatuses. Some devices add a constant amplitude noise to the antenna signals. The sampled noisy antenna signal is compared with a reference signal and the detected difference is a noted response. Another approach is to do a similar comparison without adding the noise. This device may be used in a terrain avoidance system for airborne use or in radiometer sensing of radiation from various regions of air space to determine air turbulence. In yet another device, an infrared detector senses the thermal gradient between the horizon and outer space for determining orientation and attitude of a platform. Still another microwave radiometer system senses various polarization components and detects differences between orthogonal components. Such device provides more information than is required for ordinary detection of the thermal contrast between sky and earth.
None of the above mentioned devices contains a means for accurate and fast determination of attitude of the platform through radiometric sensing of the horizon. Neither the noise nor the comparative techniques suffice. The sampling of regions of air space or the sensing of polarization components, though appearing sophisticated, does not provide advantages in attitude determination. Thus none of the prior art noted is satisfactory for such determination.